Immunohistological study of the depressed cutaneous DTH response in sheep naturally infected with an ovine lentivirus (Maedi-Visna virus).

The gross and immunohistological characteristics of the purified protein derivative (PPD)-induced cutaneous DTH reaction were studied in a group of sheep naturally infected with Maedi-Visna virus (MVV), and compared with reactions obtained in a matched control group. There was a marked, but variable, depression in the DTH lesion in the MVV group associated with a decreased density of polymorphonuclear neutrophils (PMN) and CD4+ cells in the early reaction. There were no significant differences in the densities of CD8+, gamma/delta T cells, macrophages, B cells and MHC class H-expressing cells. This work indicates that there is a significant alteration in the initial trafficking of PMN and CD4+ cells into a DTH response area in sheep infected with MVV.